The separation of an oil film from the surface of a supporting liquid such as water can be accomplished by rotating a disc at low speed in a position where it intersects the surface of the liquid, followed by wiping the adhering oil from the disc into a drainage trough. An example of this type of device is shown in the application of Harold J. Baer and Glenn B. Morse, application Ser. No. 551,161, which is pending in the U.S. Patent and Trademark Office at the time of the filing of the present application. The application here referred to provides for the removal of the oil film from the rotating disc with strips that are preferably flexible, and are attracted to the disc by magnetic forces. The conventional form of the rotating-disc machine prior to the development of the magnetic wiping arrangement provided for spring-loaded wiping devices of various types, which generated certain problems that appear to be inherent.
Another type of oil-recovery device centers in the action of an endless belt having generally vertical courses passing around a pulley or roller immersed in the composite liquid. Oil film adhering to the upward course is removed usually by some sort of wiping device, where it passes into a drainage trough. Examples of United States Patents showing oil-recovery devices described in these general terms are identified as follows:
______________________________________ Kosar, et al. 3,358,838 1967 Farrell, et al. 3,804,251 1974 ______________________________________
A very large field of application of these oil-recovery devices is in association with factory machinery in which water-base coolant becomes intermixed with lubricating oil in the machine. The supply tank associated with the coolant system thus becomes contaminated with an oil film, which eventually becomes rancid and produces a number of problems which need not be enumerated here. A recovery device is usually installed at the rim of the accumulating tank, where it can be clamped very conveniently in operating position. A disc-type device is highly effective because of its simplicity wherever such an installation can be made with the disc intersecting the surface of the composite liquid. Where the liquid level is far below the rim of the accumulating tank, or where the level is subject to large fluctuation, the diameter of a disc device required for that installation becomes excessive. In these situations where it is necessary to elevate the oil for a substantial distance to the position where it is ultimately transferred to a drainage trough, a belt system is particularly effective. Obviously, a very considerable height can be accommodated without producing a transverse dimension that becomes impractical. Belts are difficult to wipe as cleanly as discs, however, and there would be considerable advantage in a machine which could utilize the elevating capabilities of the belt in conjunction with the wiping capabilities of the disc machine. It would also be highly desirable to have such a machine capable of convenient separation between the belt and disc systems, so that the elevating device need only be installed as an attachment to a standard disc machine where it appears to be necessary to do so.